Lactic acid bacteria are a group of microbes that produce and metabolize the sugar lactate. These bacteria live in many different parts of your body including your gut, mouth, skin, genital tract and nose. These bacteria have a massive effect on the health of your body. In fact, the human body has 39 trillion bacteria living within it and is called your microbiome. The microbiome is a huge network of microbes that are involved in many functions including the breakdown of food, production of vitamins and regulation of hormones.
It is estimated that up to 80% of women with BV have imbalances of the bacteria that normally live in their vagina. These imbalances can lead to symptoms such as a white discharge with a strong fishy smell or painful sores on the vulva. If left untreated BV can increase your risk of pelvic inflammatory disease (PID), early pregnancy loss and low birth weight babies.
The bacterium that produce the lactic acid are called lactobacillus and they are found naturally in the vagina of reproductive age women. The lactic acid produced by these bacteria is the main acid present in the vaginal fluid of women of reproductive age and is responsible for the acidic pH of the vagina.
When lactobacillus is dominant in the vaginal microbiome, the acidity of the vaginal fluid is maintained at a normal level with a pH of around 7 (Linhares et al 2011).
Vaginal epithelial cells are rich in glycogen and release it into the vaginal fluid where it is metabolized by the lactobacilli to produce lactic acid. Lactic acid is also produced by the colonic bacteria during digestion. This lactic acid can be absorbed in the blood and can cause Type B Lactic Acidosis. This form of acidosis can be caused by underlying diseases such as diabetes, taking nucleoside reverse transcriptase inhibitors in HIV treatment or using metformin to treat diabetes. It is also caused by drinking excess amounts of alcohol or having an infection that affects your intestines or urinary tract.
Lactic acid has a number of beneficial properties for the female genital tract. In the vulva, lactic acid inhibits yeast overgrowth, increases barrier function and reduces inflammation. In addition, it stimulates the expression of the anti-inflammatory cytokine interleukin-17A in the lower genital tract. IL-17A stimulates macrophages in the lower genital tract to kill cancer cells and prevents recurrence of ovarian cysts (Bergeron et al 2010).
In a recent study, we examined the effects of adding lactobacillus to the diet of women who had BV or vulvovaginal candidiasis by measuring the concentrations of D- and L-lactic acid and matrix metalloproteinase inducer (EMMPRIN) in vaginal samples. Concentrations of d-lactic acid were correlated with EMMPRIN, but not with MMP-8. Our findings suggest that the relative levels of d- and l-lactic acid in vaginal samples are important in determining whether candida, BV or CTV is diagnosed. Further investigation is needed to identify the best dose and formulation of a probiotic containing lactobacillus for treating or preventing BV.